On June 8, 1943 Mutsu suffered an internal magazine explosion causing the battleship to sink into Hiroshima
Bay off Hashirajima Island. The exact cause
of the explosion was never determined, but was probably
due to the detonation of a cordite charge. Of the crew of 1,471 a total of 1,121 were killed and only 350 survived. While sinking, the battleship capsized, weighed down by its enormous superstructure. The turrets, held in place remained attached to the ship.

SalvageA failed salvage attempt happened in 1949. Salvage operations between 1970 - 1978 recovered
items include part of the bow, the anchors, screws, rudder, main guns,
the complete number 4 turret, and personal effects of the crew. Overseen by Yagi, a salvage diver who had served on the Hakki Maru. The crane used had a 1,500 ton lifting capability. The intact No. 4 turret had to be freed with explosive charges, then fell to the sea floor, and could be rigged for lifting. The turret weighed 900 tons and fired a 40cm shell.